If I have a RMC75P-MA2 with a EXP70-A2 could I setup the first SSI input as a position ref. and use the output with one of the analog inputs for another axis?
This would give me a SSI input as a position ref. an SSI axis and an Analog axis.
Will you ever have an SSI EXP module ?
Yes, you can arrange the axes in that way. In fact, you can arrange them any way you wish, which means you can shoot yourself in the foot. What you are doing is fine.
We don’t have any plans for an SSI expansion module. Most people who have wanted one can do what you are doing.
Jacob Paso
I see now. I just wasn’t adding the 1/2" axis for pos ref.
I’m thinking that I can add a SSI splitter and do gearing between two controllers.
How does an SSI splitter work? I am not sure it will work with the RMC. The RMC sends out a clock signal and expects the data to be sent back during the clocking. You can go with a quadrature encoder, and use the Q1 module, which is specifically designed to be daisy-chained so you can sync many RMCs off one encoder. If you need asbolute, you can get absolute quadrature encoders.
Jacob Paso
Good question. I am working from someone else’s information
Take a look here
http://www.plctalk.net/qanda/showthread.php?t=24765
Did I miss something? If so I may need to rethink some projects. I’m getting several (2-3) requests where I would need to do this. One customer may be late this year. I think I should be able to use the RMC150 with Profibus for that. However I don’t want to count on it being ready.
We do make a board that does that. It is the exact same board as the RMC100 SSI module, but with different jelloware in it (not sure if it’s the FPGA or what). So it fits in the RMC100 backplane like any other module. What it does is takes the SSI signal in on the first channel (the first axis’ input), then sends it out on the other one. Notice that the first input can still be used as normal feedback for control. The module basically reverses the clock and data signal on the second channel ( the axis 1 connector) to send the information out. Notice that it can only send that signal out to one other SSI input.
This method is useful when absolutely needed, but it eats up one SSI input. The signal that is sent out is also delayed by one loop time. It can only be used on the RMC100 (although the SSI signal it sends out can of course go to any other RMC). I don’t remember if the RMC150 supports it.
In general, you are better off looking at quadrature encoders for syncing multiple RMCs.
Jacob Paso
I see. Thanks for clearing that up for me.